I would also like to suggest our BlackAdder product which is a GUI IDE for 
Python and Ruby that runs on Linux and Windows and uses the Qt windowing 
toolkit.  It also makes use of our Qt port of Scintilla which has the Ruby 
features mentioned before.

BlackAdder is on beta 3 right now and the Ruby support is new in this 
release, so we are working on getting the packaging set up properly, but 
other than the lack of debugger support, it is quite nice.  You can see it 
at www.thekompany.com/products/blackadder

Regards,

Shawn Gordon
President
theKompany.com
www.thekompany.com
949-713-3276